The invention relates to a control system and method for controlling at least one function of an object, in which measures for preventing an unauthorized use or access to the object are taken. The invention also relates to an access control and driving authorization device for a motor vehicle.
Access control systems, immobilizer systems, or other control systems whose functions are enabled or controlled only when there is proven authorization of a code transmitter, for example, in the form of a Smart Card or an electronic key that is interrogated by wireless communication, are known for motor vehicles. See, for example, U.S. Pat. No. 4,763,121 to Tomoda et al. Usually, to accomplish this purpose, at least one base station with a transceiver unit, i.e., for controlling the access control or the immobilizer device, is disposed on or in the motor vehicle. In reaction to a triggering event, for example, the activation of a door handle or an ignition starter knob, an interrogation code signal is emitted at regular or irregular intervals. An authorized code transmitter, carried by the user and serving as a key, responds to the interrogation code signal with a response code signal. Such communication is also referred to as an interrogation/response dialog.
The base station checks the received response code signal in terms of its authorization, for example, by comparing a code information item contained in the response code signal with a stored reference code information item. If authorization is given, the desired function is carried out, for example, the motor vehicle doors are unlocked or the immobilizer is released.
In such a system, there may also be security problems, for example, as a result of unauthorized monitoring and deliberate modification of the wireless communication between the motor vehicle and the code transmitter. To solve these problems, there exists a device for controlling functions of an object, in particular, the access and driving authorization control for a motor vehicle. See, i.e., German Patent DE 196 32 025 C2. In the device, the length of the communication of the interrogation/response dialog is measured and is compared with a predefined maximum duration. However, the signal propagation times are very short in comparison with the computing times, with the result that prolonged signal propagation times are not evident. Therefore, the signal propagation times cannot be used as a protection against deliberate data modification by unauthorized parties.
It is accordingly an object of the invention to provide a control system and method for controlling at least one function of an object and access control and driving authorization device for a motor vehicle that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that has an increased level of protection against unauthorized attempts at use, without requiring considerable interventions into the system, and that provides an improvement in comparison with unauthorized execution of the associated function.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a control system for controlling at least one function of an object, including a base station disposed at an object and having a transceiver unit with a transmitter unit formed to transmit an interrogation signal, a portable code transmitter formed to emit a response signal with a code information item in response to the interrogation signal, the base station checking an authorization of the code information item contained in the response signal and, in the case of an authorized response signal, the base station enabling an object-specific function, at least one of the base station and the code transmitter determining a time period between a transmission of at least one part of the interrogation signal and a reception of a part of the interrogation signal obtained in reaction to the interrogation signal, and comparing the time period with a predefined reference time period, the base station enabling the object-specific function only if the measured time period is shorter than the reference time period even if the code information item of the response signal is correct, an evaluation circuit in at least one of the code transmitter and the base station for evaluating the code information item, a transmitter antenna, and a bypass path through which parts of the interrogation signal are routed to the transmitter antenna, the bypass path bypassing the evaluation circuit.
In the invention, the time period between the transmission of marked parts of a transmit signal and the reception of these parts is determined in one of the units involved. For example, the system reaction time is measured in order to determine the distance between the code transmitter and the base station disposed at the object end. The measurement is preferably carried out in the base station for reasons associated with power technology, logic, or the system, but depending on the system configuration the code transmitter can also perform it.
When there is an unauthorized remote interrogation, the very much longer signal paths and the internal processing times of the intermediately connected signal amplifiers result in significantly longer processing times than in the case of an authorized code transmitter that is located near to the motor vehicle, and, thus, longer delays between the emission of the signal and the reception of the response signal. In such a case, the evaluation circuit measures the time period between the emission of the signal and the reception of at least one or more marked sections or parts of the signals, and compares these time periods. In the simplest case, the time period is compared with a previously defined reference time period that is sufficient for the signal to be received back from an authorized code transmitter located near to the motor vehicle, but is usually exceeded in the case of an unauthorized remote interrogation due to the above mentioned influences.
The base station is configured according to the invention such that it executes or enables the desired function only if at least the particularly characterized parts of the signals have been received within the predefined time period.
In order to eliminate internal time delays that are due to the system and cannot be calculated preciselyxe2x80x94especially long time delaysxe2x80x94and which are caused by the processing operations, necessary at the receiver end (for example, code transmitter end), which relate to the reception of an interrogation signal, the detection and evaluation of the interrogation signal, the generation/calculation of a response signal and its emission, the system component which generates the response signal (here the code transmitter) is preferably equipped with a bypass path through which at least a marked part of the received signal can be conducted directly to the transmitter (transmitting amplifier and/or antenna), bypassing the system component""s own evaluation circuit, and thus transmitted back, virtually without delay, to the component that transmitted the signal.
The appropriate parts are reflected without delay, apart from the short group delay (transparent mode of the code transmitter). The delay between the emission and reception of a signal is then essentially only conditioned by propagation time so that a distance measurement takes place between the base station and the code transmitter. Additional analog or digital processing of the original signal would entail additional processing times that would be significantly longer than the signal propagation time in free space.
In accordance with another feature of the invention, there is provided at least one switch disposed in the bypass path and formed to selectively disconnect and connect the bypass path into the evaluation circuit.
The bypass path is preferably provided with a controllable switch so that the bypass path causes parts of the received signal to be forwarded directly to the transmitter only on a temporary basis, but can otherwise be switched off. Thus, it does not adversely affect the signal communication (and the energy content) of the received signal.
In accordance with a further feature of the invention, at least one of the code transmitter and the base station is formed to apply the received interrogation signal at least temporarily to the evaluation circuit and to the bypass path in parallel.
In accordance with an added feature of the invention, the evaluation circuit is formed to add an additional signal to signals conducted to the transmitter antenna through the bypass path.
In accordance with an additional feature of the invention, at least one of the base station and the code transmitter are formed to emit at least one pulse transmitted back to the transmitter unit through the bypass path and the transmitter antenna.
If the component that is equipped with the bypass path applies the received signal not only to the bypass path but also at the same time to its own evaluation circuit, the evaluation circuit can check the received signal to determine whether or not the code that is intended for the respective component is correct. If the code (or code information) is correct, the evaluation circuit can add on an additional signal, for example, a pulse or a pulse sequence, to the signal that has been conducted through the bypass path and transmitted. The configuration permits, to an even greater extent, the protection against deliberate data modification, for example, against the use of falsified transponders.
In accordance with yet another feature of the invention, at least one of the base station and the code transmitter is formed to emit at least one of a pulse and a code sequence and to modulate at least one of an amplitude, a pulse length, and a frequency of the at least one of a pulse and a code sequence, and the evaluation circuit is formed to measure a time period between an emission and a reception of the at least one pulse and code sequence, and to check at least one of the amplitude, the pulse length and the frequency of the at least one pulse and code sequence.
In accordance with yet a further feature of the invention, at least one of the base station and the code transmitter is formed to be configured for a plurality of at least one of frequency bands and a plurality of channels within a frequency band, and is formed to change a transmission frequency respectively being used.
In the multichannel mode of operation, or when there are generally a plurality of transmission paths between the motor vehicle and the identification component (code transmitter or transponder 1), the mode of operation described above can also be carried out simultaneously with the actual exchange of code. The simultaneous operation makes deliberate data modification even more difficult.
The component that generates the interrogation code signal preferably generates the additional pulse or pulses or else the interrogation code signal with a field strength, pulse length, frequency, sequence, pulse duty factor that changes from pulse to pulse or signal to signal. When the pulses are conducted through via the bypass path, the information arrives back, in addition to the component that generates the interrogation code signal, in the form of corresponding differences in field strength, pulse length, or frequency, so that an additional security parameter is made available, the security parameter is evaluated by the component generating the interrogation code signal by comparing the received profile of the field strength, pulse length, or frequency with the anticipated profile. In the case of remote transmission, it is virtually impossible to produce these parameters precisely so that deviations of the received profile from the actually expected profile constitute an additional indication of unauthorized vehicle use.
If a plurality of transmission channels/frequency bands is present, an additional increase in security in comparison with unauthorized access or use can be achieved by changing the transmission frequencies used. During the vehicle locking operation, the transmitter unit can, for example, feed to the code transmitter an item of information that signals the transmission frequency that is to be used during the following opening or starting operation, and the code transmitter then sets itself to that frequency. Therefore, during a subsequent opening operation, the transmitter of the code transmitter is set to the correct frequency. Such setting allows the pulses that are conducted through the bypass path to be conducted back on the correct frequency or the correct channel virtually without delay and without transient response processes or the like.
To the extent that the response code signal obtained from the remotely disposed code transmitter can at all be transmitted correctly over the remote interrogation path, the response code signal is still generated with a considerable time delay. Based upon the considerable time delay, the base station can clearly distinguish between a signal transmitted back by a code transmitter that is in situ and a signal that has been fed by unauthorized remote interrogation. Unauthorized remote interrogation can be performed, for example, by predefining, again, a time window for the response signal that has already closed when the response signal, that is fed severely delayed or distorted over the remote interrogation path, is received. Such results in a rejection of the response signal because it has arrived with too great a delay.
Instead of the transmission frequency being predefined as the next parameter to be selected, a different signal parameter, for example, the amplitude, method of modulation, or the like can also be set by the base station.
In the invention, increased signal propagation times between the base station and remotely disposed code transmitters are used to distinguish between a code transmitter that is located in situ, i.e., near to the motor vehicle, and a remotely disposed code transmitter, which is thus interrogated without authorization, and to execute or enable the function of the vehicle only if the code transmitter is an authorized one that is located in the vicinity of the vehicle.
The invention can generally be used not only in controlling the access control function or immobilizer function, but also in other functions that are to be executed only when an authorized key is present. The invention can generally be used in the authorization-related control of object functions that do not relate to motor vehicles, for example, access control to houses, apartments, offices, hotels, multistory car parks, garages, and the like.
To implement the invention in the simplest case, all that is required is for a time window function to be added to the base station by programming (the time period between the emission and reception of parts of signals is measured and the recorded time period is compared with a predefined time value). When a bypass path is added to the code transmitter, all that is necessary is to configure the code transmitters appropriately, which does not involve a large amount of work or high cost. Thus, the invention can be implemented easily and cost-effectively without the necessity for high levels of system intervention, and can be applied in different system configurations without any disadvantages occurring during use, including driving mode (for example, in respect of reaction times, operating reliability, etc.).
With the objects of the invention in view, there is also provided a method for controlling at least one function of an object, including the steps of carrying out an authorization check between a portable code transmitter and a base station disposed at an object by transmitting, through a transmitter, an interrogation signal in at least one pulse modified in at least one of amplitude, pulse length, and frequency, receiving the interrogation signal through a receiver having a transmitter circuit, the receiver conducting the at least one pulse to the transmitter circuit through a bypass path without evaluation processing, transmitting through the transmitter circuit the at least one pulse and a response signal containing a code information item, receiving the at least one modified pulse and the response signal, measuring a time period between an emission of at least one part of the interrogation signal and a reception of a part of the response signal obtained in reaction to the interrogation signal, comparing the time period with a predefined reference time period, determining whether or not the code information item contained in the response signal is an authorized code information item, and enabling or carrying out a function only if the authorized code information item is determined to have been received and if the measured time period lies within the predefined reference time period.
In accordance with yet an added mode of the invention, there are provided the steps of evaluating within the response signal at least one of parts of the interrogation signal conducted through the bypass path, a length of the parts of the interrogation signal conducted through the bypass path, and a position of the parts of the interrogation signal conducted through the bypass path, and comparing the parts of, the length of the parts of, and the position of the parts of the interrogation signal conducted through the bypass path with anticipated values.
With the objects of the invention in view, there is also provided a method for controlling at least one function of an object, including the steps of carrying out an authorization check between a portable code transmitter having a portable receiver, a bypass path, and a transmitter circuit, and a base station disposed at an object, the base station having a base station transmitter, a base station receiver, and a control unit, by transmitting, through the base station transmitter, an interrogation signal in at least one pulse modified in at least one of amplitude, pulse length, and frequency, receiving the interrogation signal through the portable receiver, the portable receiver conducting the at least one pulse to the transmitter circuit through the bypass path without evaluation processing, transmitting through the transmitter circuit the at least one pulse and a response signal containing a code information item, receiving with the base station receiver the at least one modified pulse and the response signal, measuring with the control unit a time period between an emission of at least one part of the interrogation signal and a reception of a part of the response signal obtained in reaction to the interrogation signal, comparing with the control unit the time period with a predefined reference time period, determining with the control unit whether or not the code information item contained in the response signal is an authorized code information item, and at least one of enabling or carrying out a function with the control unit only if the authorized code information item is determined to have been received and if the measured time period lies within the predefined reference time period.
In accordance with a concomitant feature of the invention, there is also provided an access control and driver authorization device for a motor vehicle, including a base station disposed at a motor vehicle and having a transceiver unit formed to emit an interrogation signal and to subsequently wait for and receive a response signal, the transceiver unit having a control unit with an evaluation unit and a timer device formed to evaluate respectively the response signal for authorization and signal propagation time, and a portable code transmitter having a receiver formed to receive the interrogation signal, an arithmetic unit, a bypass path, a transmitter formed to transmit the response signal after the interrogation signal has been received, and a switching device formed to switchably connect the transmitter to the receiver through at least one of the arithmetic unit and the bypass path and formed to conduct predefined parts of the received interrogation signal directly from the receiver to the transmitter through the bypass path and to conduct a remainder of the request signal to the transmitter through the arithmetic unit, such that, when authorization is confirmed by the control unit and the signal propagation time is confirmed by the control unit, the base station performs at least one of permitting access to the motor vehicle and releasing a motor vehicle immobilizer.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a control system and method for controlling at least one function of an object and access control and driving authorization device for a motor vehicle, it is, nevertheless, not intended to be limited to the details shown since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.